Fuel cells in which fuel and oxidant react to produce electricity and water are well known in the art. Electricity is generally produced at a catalyst/electrolyte, which usually forms a common wall separating an anode chamber and a cathode chamber. A fuel, such as hydrogen, is introduced to the anode chamber, while an oxidant, such as oxygen or air, is introduced to the cathode chamber. In a Membrane Fuel Cell operating on hydrogen and oxygen, for example, the hydrogen is ionized at a catalyst, forming hydrogen ions and free electrons. The ions pass through the ion exchange membrane and react with oxygen to form water. In a Molten Carbonate Fuel Cell, on the other hand, oxygen reacts with carbon dioxide to form carbonate ions. The ions cross the ion exchange membrane where they react with hydrogen form water, carbon dioxide, and free electrons.
Although the exact reaction which produces electricity in the various fuel cells; Membrane Fuel Cell, Phosphoric Acid Fuel Cell, Molten Carbonate Fuel Cell, Solid Oxide Fuel Cell, or Alkaline Fuel Cell (hereafter referred to as fuel cell), may differ, all of the overall reactions are exothermic; producing waste heat.
In order to allow a fuel cell to operate continuously, the waste heat must be removed. Cooling, by altering the phase of a substance, typically water, from the liquid to the gaseous phase by addition of heat, can be employed to accomplish this task.
Various fuel cell cooling methods have been developed. U.S. Pat. No. 4,344,849 (incorporated herein by reference) discloses a technique which consists of passing water through separate coolant passages within the fuel cell. Some of the water is converted to steam; creating a two phase steam/liquid mixture. The steam and liquid are separated, the steam for use in the reformer and the water for recycle. U.S. Pat. No. 4,795,683 (incorporated herein by reference), discloses a technique of cooling a fuel cell by supplying a controlled amount of liquid water, as mist, to the anode, transporting the water through the ion exchange membrane to the cathode, and evaporating the water.
An object of the present invention is to provide a more efficient coolant process for use within a fuel cell system.